As is well known, port fuel injectors in internal combustion engines can become fouled due to the formation of deposits. Such fouling can adversely affect engine performance. For example, deposits on port fuel injectors can restrict fuel flow and disrupt spray patterns by partially obstructing or plugging up metering holes of the injector tip. There has been considerable work devoted to additives for effectively controlling engine deposits. However, this work has tended to focus primarily on intake valve deposits and, to some extent, on combustion chamber deposits. Many additives, which may be effective in reducing intake valve deposits and combustion chamber deposits, are not effective at preventing port fuel injector fouling. This is believed to be due to, for example, the differences in the temperatures of the different engine regions; the port fuel injectors being considered a so-called “cooler” engine region than the intake valves and combustion chamber. Additionally, many deposit control additives perform only as long as the additive is being used, i.e., is passing through the injector. Thus, the port fuel injectors become quickly fouled once a fuel which does not contain deposit control additives or effective deposit control additives is passed through the port fuel injectors.